The motor controller that drives and controls an electric motor of the electric power steering device mounted on a vehicle, an electric motor of an electric brake system, or an electric motor for travelling of an electric vehicle or a hybrid vehicle is demanded to continuously drive the electric motor, even if an abnormality occurs at the motor control system.
To meet the above demand, for example, a double system of the multiphase motor windings of the multiphase electric motor are provided, current is supplied to the multiphase motor windings in the double system from the individual inverter parts. When there arises an off failure, namely an open failure, in which switching means of one of the inverter parts cannot be electrically conductive, there is a proposal for a controller of a multiphase rotating machine and an electric power steering device using the controller (for example, see patent literature 1), the controller including failure-time control means that identifies the failed switching means where such a failure occurs, controls to exclude the failed switching means, and controls a normal inverter part except for the failed inverter part including the failed switching means.